Playing with this decklist right now.
It was actually a top-down design - I wanted to focus on my academic interests, those being oceanography and biology. I identified biology mechanically resonant, as there already exist several cards which focus on evolution and growth.
R/U/G (or Ceta, as I am still more than willing to call it) is the perfect color combination for this. Oceanography is, in short, every single science, and R/U/G unites the colors of Ravnica’s two science guilds: the Simic Combine and the Izzet League.
From there, I attempted to find mechanical overlap between the two guilds which I knew would work for the deck. Storm Entity and Nivmagus Elemental were the two cards that were the focus of this phase of deckbuilding: they unify Simic’s +1/+1 counters with Izzet’s affinity for Instants and Sorceries.
Proliferate was included as a nod to the Progress Engine’s own scientific leanings, as well as the mechanical synergy which existed between the strong ‘+1/+1 counters matters’ theme and proliferate itself.
Slivers were admitted to the deck because they as a tribe exude the idea of evolution and, well, ‘adaptive radiation.’
Mechanically, it plays quite well. I have won both games I have played with it, but still hope to tune it further. And maybe drive the cost of buying physical cards down, as well.